Safety device

ABSTRACT

A safety device, comprising a connection point ( 21 ) for a pressure accumulator ( 1 ) that is connected to a bursting unit ( 55 ) at the gas end via the connection point ( 21 ), is characterized in that the bursting unit ( 55 ) can be triggered by a controllable force element ( 73 ) and, in the triggered state, allows the pressure accumulator ( 1 ) to be emptied at the gas end.

The invention relates to a safety device comprising a connection point for a pressure accumulator that is connected to a bursting device at the gas side via the connection point.

Such safety devices are state of the art. In systems, in which gaseous working media are used, safety devices of this type are employed to obtain a safe, i.e. not environmentally hazardous pressure reduction in the event of a problem. In particular in the case of systems which contain pressure accumulators, which during operation produce high gas pressures that can be 100 bar or higher, it is necessary to ensure that, when there are pressure increases exceeding a safe limit value, of the kind produced by operation interruptions due to malfunction of system components or due to temperature increases, for example in the case of a fire, a safe pressure reduction takes place through activation of the bursting device.

Given this prior art, the problem addressed by the invention is to provide a safety device which ensures a particularly safe activation of the bursting device assigned to a pressure accumulator.

According to the invention, this problem is solved by means of a safety device having the features of claim 1 in its entirety.

Because, according to the characterizing part of claim 1, the bursting device can be triggered by means of an actuatable force element, by contrast with the prior art where the bursting device is activated simply when an excess pressure exceeding a given value is reached, a triggering can occur in the case of a problem or in a hazardous situation without excess pressure prevailing or even before the excess pressure is reached. This makes it possible to react to hazardous situations, for example in the case of a fire, with a pressure reduction before a dangerous excess pressure is reached due to heating in the case of a fire. The invention is thus particularly advantageously suitable for applications in mobile systems in which pressure accumulators are present, such as in vehicles which are provided with an energy recovery device in conjunction with a hydrostatic travel drive. Such systems comprise at least one pressure accumulator which can be charged to a high pressure level for storage of braking energy, in this regard refer to document DE 10 2008 062 836 B3 for example, which presents such a drive system for utility vehicles or other vehicles which can be deployed on roads. The safety device according to the invention used in such vehicles permits a non-hazardous, preventive pressure reduction in the case of problems, for example a vehicle crash or the like.

In advantageous exemplary embodiments, the bursting device has a bursting disk which is triggered when a maximum gas-side pressure is exceeded and/or when the force element is actuated. Because the breakage of the bursting disk makes the pressure reduction take place in the case of excess pressure even without activation of the force element, the invention satisfies particularly high safety requirements.

A pyrotechnic object can particularly advantageously be provided as the force element which, when the propellant is ignited, deforms or destroys a wall section of a housing in such a way that the bursting device accommodated therein is triggered, or which destroys the bursting disk of the bursting device by means of an activation pin. While in the former case the shock wave released by ignition of the propellant itself leads to the destruction of the bursting disk, in the latter case the breakage of the bursting disk takes place by the mechanical action of a mechanical part moved by the explosion pressure of the ignited propellant.

The actuation of the force element can be coupled to a sensor system, in particular to the sensor system of an airbag, which also activates the force element when the airbag is triggered. This has the advantage that for the detection of an accident, which calls for a safe pressure discharge, there is no need for the force element to have its own sensor system.

The arrangement can advantageously be such that the bursting disk of the bursting device is fixed in a pressure-conveying channel in the housing and seals this channel in a pressure-tight manner, which channel leads to the gas side of the pressure accumulator and opens into the environment. By means of pressure from the bursting disk, a direct connection is thus formed between the gas side of the pressure accumulator and the environment.

The bursting disk can particularly advantageously lie inside the channel in the same plane as the direction of action of the pyrotechnic force element, with the wall section of the housing which can be destroyed or deformed by means of the propellant extending transverse to this plane.

In particularly advantageous exemplary embodiments, the force element carries, encapsulated on its front face side, the pyrotechnic propellant to be electrically ignited, which is connected to the wall section, on which the bursting device is at least partially laid. In this arrangement the wall section is directly exposed to the pressure shock wave produced by the propellant.

In a particularly advantageous manner, the housing can also form the support for functional elements belonging to a corresponding pressure accumulator to be rendered safe, such as a pressure sensor, a temperature sensor, a safety fuse device, a filling connection for pressurized gas and/or a test connection for a testing device. A safety fuse device, which realizes a temperature-dependent pressure release even without activation of the force element, provides an additional safety feature.

In advantageous exemplary embodiments, all of the functional elements used in the housing, including the bursting device, are connected to a common channel system, which is connected in a pressure-conveying manner to the gas side of the pressure accumulator. The overall assembly can thus be realized in the form of a compact unit.

The pressure accumulator to be rendered safe can be a piston accumulator, which is part of an energy recovery system in a motor vehicle and which, on its accumulator housing side with the pressurized gas, carries the block-like housing with its own functional elements.

The invention is explained in detail below with reference to an exemplary embodiment depicted in the drawings, in which:

FIG. 1 shows a longitudinal section of a pressure accumulator, which is provided at the gas side with an exemplary embodiment of the safety device according to the invention depicted in a schematically simplified manner;

FIG. 2 shows a top view of the exemplary embodiment of the safety device, with the top cover wall of the housing being depicted transparent;

FIG. 3 shows, depicted slightly enlarged by comparison with a practical embodiment, a partial longitudinal section of the housing of the safety device according to the exemplary embodiment of the invention;

FIG. 4 shows, depicted enlarged by a factor of 2 compared with FIG. 3, a partial section of the region identified in FIG. 3 with IV;

FIG. 5 shows, depicted enlarged by a factor of 1.5 compared with a practical embodiment and partially broken open, a side view of a pyrotechnic force element for use in the safety device according to the invention; and

FIG. 6 shows, depicted on the scale of FIG. 5 and rotated 90° relative thereto, an end view of the pyrotechnic force element of FIG. 5

FIG. 1 shows a hydropneumatic pressure accumulator 1, which can be used for example in vehicles with a hydrostatic drive that are provided with an energy recovery device in order to store braking energy, in this regard refer to the already mentioned document DE 10 2008 062 836 B3. The pressure accumulator 1 depicted in FIG. 1 is a piston accumulator, the accumulator piston 3 of which is, in a standard manner for such accumulators, provided with at least one piston seal 5 and at least one piston guide 7 and which is guided in a mobile manner inside the pressure accumulator 1. In FIG. 1 the piston 3 is depicted in a position in which the oil side 11 connected to a hydraulic connection 9 is unpressurized, so that the piston 3 is located in the end position, in which the volume of the gas side 13 has the maximum value. At the end of the pressure accumulator 1 opposite the oil side 11 there is a gas connection 15, by means of which the gas side 13 can be filled with a working gas, such as nitrogen. In an application for storage of braking energy in the case of energy recovery devices high gas pressure can occur during operation at the gas side 13, so that safety measures must be undertaken, which bring about a safe pressure reduction in the case of problems or a hazardous situation. It is thus state of the art to provide a safety device 17 at the gas connection 15 which produces a safe pressure reduction by means of activation of a bursting device.

FIGS. 2 to 4 show further details of the housing 19 of the safety device 17 according to the invention. The housing 19 has the form of a housing block with a planar top side 23 and a bottom side 25 extending in a plane parallel thereto, cf. FIG. 1. As FIG. 3 shows, the block is rectangular apart from a chamfered edge region 27. In this figure the top side 23 of the block is depicted transparent, so that inner channels, connections assigned thereto and assigned functional elements are visible in FIG. 2. This figure also shows that in the vicinity of the long side provided with a chamfer 29 a connection piece 31 projecting from the bottom side 25 (FIG. 1) is provided, in which the thread of the screw connection 21 is formed for the connection to the gas connection 15. Branching off the thus formed pressure connection is a first channel 33, which leads to a safety fuse 35 of conventional construction. On the side opposite the channel 33 a second channel 36 branches off the pressure connection, which leads to a filling connection 37, at which a filling valve 39 of conventional construction is arranged with a cover cap 41 located on the outside of the housing. A third channel 43 branches off the second channel 36 at a right angle. This third channel leads to a connection 45 for a pressure sensor 47 located on the outside of the housing and to a connection 49 for a temperature sensor 51 located on the outside of the housing.

At the point of the branch of the first channel 33 from the pressure connection an additional fourth channel 53 extending parallel to the third channel 43 branches off, which forms the connection of the bursting device 55 according to the invention to the pressure connection. FIGS. 3 to 6 show further details of the bursting device 55 and of the functional elements provided according to the invention for the controlled triggering of the bursting device 55. As FIG. 3 and in particular the enlarged depiction of FIG. 4 show, the channel 53 is separated from the outlet 59 opening at the housing side 57 by means of a bursting disk 61. This bursting disk is, as FIG. 4 most clearly shows, fixed by means of a threaded insert 63, which is screwed from the housing side 57 into a threaded hole 65 of the housing 19. The insert 63 clamps the bursting disk 61 against a shoulder 67 formed on the inner end of the threaded hole 65, with the peripheral edge 69 of the bursting disk 61 inside an annular groove 71 located at the end of the threaded hole 65 being laid around the end of the insert 63.

For the triggering of the bursting disk 61 of the bursting device 55 realized by means of an actuatable force element the present exemplary embodiment provides a pyrotechnic device having a cartridge 73, which contains an electrically ignitable propellant 75. This propellant is encapsulated in the cartridge 73 in such a way that, when the propellant 75 is ignited, an explosion pressure wave is discharged starting from the top side of the cartridge 77 with a direction of action along the cartridge longitudinal axis 79. For the electric ignition the cartridge 73 has, at the end 81 opposite the top side 77, contact pins 83 with connecting lugs 85 for ignition lines. As FIG. 3 most clearly shows, the cartridge 73 is fixed in a housing hole 91, which starts from the housing side 93, by means of a retaining ring 95, which is attached by means of screws 97 onto the housing 19.

As FIGS. 3 and 4 show, the top side 77 of the cartridge 73 with the discharge region of the explosion pressure wave is located on a wall section 87 of the housing 19, which directly adjoins the bursting device 55, with the direction of action of the explosion pressure wave which extends along the axis 79 extending in the plane of the bursting disk 61. The resulting deformation of the wall section 87, in particular in the region of the shoulder 67 clamping the bursting disk 61, leads to the destruction of the closure of the channel 53 by means of the bursting disk 61 and thus to the pressure reduction which takes place via the channel 53 in the direction of the free environment of the block. Independently of a triggering of the bursting disk 61 by means of built up excess pressure and independently of a pressure reduction brought about by excess temperature by means of activation of the safety fuse 35, the invention permits controlled triggering of the bursting device 55 based on different signaling when a problem or a hazardous situation occurs. Without additional sensors this makes it possible to use the triggering signal of an airbag in the event of a crash.

While the depicted exemplary embodiment uses the direct action of the explosion pressure wave of a pyrotechnic cartridge 73 to trigger the bursting device 55, it goes without saying that the breakage of the bursting disk 61 can be brought about by mechanical action of a mechanical force element. For example, instead of a pyrotechnic device generating an explosion pressure wave a pyrotechnic element can be provided which, when ignited, provides the drive for a mobile pin (not depicted), which destroys the bursting disk by means of mechanical action. At the same time, with the depicted direct use of the explosion pressure wave, the safety device can be realized with a simple construction at little expense. 

1. A safety device comprising a connection point (21) for a pressure accumulator (1) that is connected to a bursting device (55) at the gas side via the connection point (21), characterized in that the bursting device (55) can be triggered by means of an activatable force element (73), which permits a gas side emptying of the pressure accumulator (1) in the triggered state.
 2. The safety device according to claim 1, characterized in that the bursting device (55) has a bursting disk (61), which is triggered when a maximum gas-side pressure is exceeded and/or when the force element (73) is actuated.
 3. The safety device according to claim 1, characterized in that the force element is a pyrotechnic object (73) which, when the propellant (75) is ignited, deforms or destroys a wall section (87) of a housing (19) in such a way that the bursting device (55) accommodated therein is triggered, or which destroys the bursting disk (61) of the bursting device (55) by means of an activation pin.
 4. The safety device according to claim 1, characterized in that the actuation of the force element (73) is coupled to a sensor system, in particular to the sensor system of an airbag which, when the airbag is triggered, also activates the force element (73), preferably at the same time.
 5. The safety device according to claim 1, characterized in that the bursting disk (61) of the bursting device (55) is fixed in a pressure-conveying channel (53) in the housing (19) and seals this channel (53) in a pressure-tight manner, which leads to the gas side (13) of the pressure accumulator (1) and opens into the environment (57).
 6. The safety device according to claim 1, characterized in that the bursting disk (61) inside the channel (53) lies in the same plane as the direction of action (79) of the pyrotechnic force element (73) and in that the wall section (87) of the housing (19) which can be destroyed or deformed by means of the propellant (75) extends transverse to this plane.
 7. The safety device according to claim 1, characterized in that the force element (73) carries, encapsulated on its front face side (77), the pyrotechnic, propellant (75) which is to be electrically ignited, which is connected to the wall section (87) on which the bursting device (55) is at least partially laid.
 8. The safety device according to claim 1, characterized in that the housing (19) at least partially has additional functional elements, such as a pressure sensor (47), a temperature sensor (51), a safety fuse device (35), a filling connection (39) for pressurized gas and/or a testing connection for a testing device.
 9. The safety device according to claim 1, characterized in that all of the functional elements used in the housing (19), including the bursting device (55), are connected to a common channel system (33, 36, 43, 53), which is in a pressure-conveying connection with the gas side (13) of the pressure accumulator (1).
 10. The safety device according to claim 1, characterized in that the pressure accumulator is a piston accumulator (1), which is part of an energy recovery system in a motor vehicle and which, on its accumulator housing side (13) and with the pressurized gas, supports the block-like structured housing (19) with its own functional elements. 